We used to think the voting system was something like the traffic laws — a set of rules clear to everyone, enforced everywhere, with penalties for transgressions; we used to think, in other words, that we had a national election system. How wrong a notion this was has become painfully apparent since 2000: As it turns out, except for a rudimentary federal framework (which determines the voting age, channels money to states and counties, and enforces protections for minorities and the disabled), U.S. elections are shaped by a dizzying mélange of inconsistently enforced laws, conflicting court rulings, local traditions, various technology choices, and partisan trickery.

In some places voters still fill in paper ballots or pull the levers of vintage machines; elsewhere, they touch screens or tap keys, with or without paper trails. Some states encourage voter registration; others go out of their way to limit it. Some allow prisoners to vote; others permanently bar ex-felons, no matter how long they've stayed clean. Who can vote, where people cast ballots, and how and whether their votes are counted all depends, to a large extent, on policies set in place by secretaries of state and county elections supervisors — officials who can be as partisan, as dubiously qualified, and as nakedly ambitious as people anywhere else in politics. Here is a list — partial, but emblematic — of American democracy's more glaring weak spots.

#1 The New Poll Tax
Atlanta, Georgia

In 2005, Georgia state legislators passed a bill requiring voters to present either a driver's license or a state-issued photo ID that costs between $20 and $35 and is available only from Department of Motor Vehicles offices. Supporters claimed this was necessary to keep people from casting votes in someone else's name, even though Georgia secretary of state Cathy Cox noted that her office had no evidence of this happening. Either way, the measure is likely to have a dramatic effect on who can vote. Two-thirds of the state's counties don't even have a DMV office; Atlanta, the state's largest city, has just one, where waits at the ID counters often run to several hours. In late June, the secretary of state issued a report finding that more than half a million active-status, registered voters in Georgia don't have valid photo IDs. Fully 17.3 percent of African American voters, and one-third of black voters over age 65, wouldn't be able to cast a ballot under the law. When the federal Department of Justice had five experts examine the ID legislation in 2005, four of them objected to it, as the Washington Post discovered. But higher-ups at Justice overruled them and the measure (pushed by conservative think tanks such as the American Center for Voting Rights) went on the books. In October of last year a judge blocked its implementation, and the law — along with another version that offers free voter IDs — remains in limbo as appeals continue.

At least two other states, Wisconsin and Missouri, have passed similar ID legislation. (Wisconsin's governor has since vetoed it.) University of Wisconsin-Milwaukee professor John Pawasarat has found that fewer than a quarter of 18-to-24-year-old black men in that state have valid driver's licenses, the most common state-issued ID. In Indiana, a new law requires valid IDs to bear an expiration date, ruling out Veterans Affairs cards, among others.

"In my view it's an orchestrated vote-suppression strategy by less scrupulous strategists in the Republican Party," says Dan Tokaji, associate director of election law at Ohio State University's Moritz College of Law. "It's pretty clear to me that these are disenfranchisement strategies. I try not to use that word too often, but in this case it fits."

Runner-up: Arizona voters in 2004 passed Proposition 200, which requires "proof of citizenship" when a person registers to vote. There's no evidence that noncitizens had been flocking to the polls, but the measure is bad news for Native Americans, the poor, and the elderly, who often don't have the requisite documents. Driver's licenses issued prior to 1996 don't count — a not-insignificant fact, given that Arizona licenses are valid until a person turns 65. Officials say that 14,000 voter registrations in Phoenix and environs have already been rejected because of the law.

In 2004, a touch-screen voting machine in Beaufort, North Carolina, erased 4,439 ballots cast during early voting two weeks before Election Day; they were never recovered. A similar problem in Burke County, North Carolina, resulted in several thousand votes for president not being counted. And, according to the San Francisco-based Electronic Frontier Foundation, a voting machine in Ohio managed to add 4,000 extra votes for Bush. But those episodes, voting experts say, are just a preview of balloting debacles to come: The federal Help America Vote Act requires most counties to replace punch-card or lever machines with newer technology by the end of this year, and election officials are scrambling to meet the deadline. Already during this spring's primaries, reports of trouble multiplied: Initial results in Fort Worth, Texas, showed 150,000 votes being tabulated in a county where only about 50,000 people voted. In Pottawattamie County, Iowa, machines suddenly began counting some candidates' votes backward. In Philadelphia, more than 5 percent of voting machines broke down on primary day.

The most sensational claims about voting technology have to do with the possibility of actually programming the machines to manipulate elections; computer scientists have warned that viruses could, for example, be inserted into vote-counting programs to delete a set number of votes and then erase themselves. So far no smoking guns have been found to prove such vote-fixing. But there have been myriad well-documented instances of human error and machine failures, and of extreme reluctance on the part of machine manufacturers to make their software accessible to outside experts. "Elections in this country are becoming proprietary," explains Lillie Coney, coordinator of the D.C.-based National Committee for Voting Integrity. "Vendors are saying, 'You can't investigate our technology, or our software.' They've put the technology in place, but the mechanisms for public officials to manage the technology, they're just not there."

When Ion Sancho, the elections supervisor in Leon County, Florida, discovered last year that Diebold's machines could easily be tinkered with, the company responded by refusing to service or upgrade the county's voting equipment so long as Sancho remained in charge. Since then, researchers in Florida and California have discovered more problems with Diebold technology, finding that the machines could accidentally allow one person to cast multiple votes, could be tricked into terminating an election count before all the votes had been tallied, and could permit changes to election results without detection.

Even some of the "paper trail" systems for electronic voting are deeply flawed. On some machines, logs have been designed so badly that auditors are at risk of counting "tentative" votes instead of the voters' final choices; on others, a voter wanting to check whether her choice has registered must lift an inconspicuous door and then peer, through a plastic screen, at a tiny printout, with the actual vote often not even scrolling into view.